Compression ignition internal-combustion engine



L. o. FRENCH 2,662,510 COMPRESSION IGNITION INTERNAL-COMBUSTION ENGINE Dec. 15, 1953 Filed Dec. 18, 1950 IN V EN TOR.

Patented Dec. 15, 1953 COMPRESSION IGNITION INTERNAL- COMBUSTION ENGINE Louis 0. French, Milwaukee, Wis. Application December 18, 1950, Serial No. 201,362 3 Claims. (01. 123-32) The invention relates to compression ignition internal combustion engines and more particularly to an open type combustion chamber.

The invention is for an improvement on that form of open type combustion chamber in which the chamber is, except for a working clearance, formed by an open cavity Wholly within the piston into which fuel is injected near the end of the compression stroke. Chambers of type also act in conjunction with an induction swirl, either by the use of mashed inlet v lve or its equivalent in a four cycle engine or t ntially disposed inlet ports in a two cycle engine which swirl is augmented by the active squish action of the air produced by the small clearances between the annular top portion of the piston surrounding said chamber and the cylinder head. Combustion chambers as described above and generally known as toroidal chambers have been quite widely used, especially in England, in motor vehicle engines but have certain recognized drawbacks. Such open type chambers have a longer ignition delay period than the so-called swirl type chamber using compression pressure induced swirl, they are more critical of the quality of fuel used as compared to the swirl chamber and precombustion chainber types, and they require the use of high injection pressures usually through multi-orifice nozzles. The object of the present invention is to provide certain modifications in the structure of the open type chamber above described by which the ignition delay period will be reduced, and a wider choice of fuels and less sensitive fuel injection equipment may be used.

A further object of the invention is to provide a combustion chamber of the type above described in which in place of the usual centrally disposed integral projection at the bottom of the chamber, a hot surface ignition tube or supplemental chamber is used and preferably one that acts as a burner for that portion of the fuel charge forced into it during the compression stroke, the action of this tube aiding in the heating of the injected fuel and the mixing of the fuel with the air.

The invention further consists in the several features hereinafter set forth and more par ticularly defined by claims at the conclusion hereof.

In the drawings:

Fig. l is a vertical sectional view through an internal combustion engine equipped with a combustion chamber embodying the invention;

Fig. 2 is a View similar to 1 showing certain modifications;

Fig. 3 is a detailed horizontal sectional View taken on the broken line ii-3 of 1.

Referring to the drawings, the numeral desighates the cylinder of the engine, ii the cylinder head, and i the piston mounted as usual for reciprocation in the cylinder. As shown in Fig. 1, the head is provided with an air inlet port 8 con-- trolled by an inlet valve and an exhaust port it controlled by an exhaust valve ii. For producing an induction induced swirl, the inlet valve it is provided with a mask i2 which functions in known manner to impart a swirling motion to the air passing into the cylinder. The mask is illustrative of one form of means for inducing swirl in a four cycle engine. In a two cycle englue, the scavenge air inlet ports are tangentially inclined relative to the cylinder bore for this purpose. A fuel injector is of any suitable form is mounted in the cylinder head and may be provided with either a multiple hole nozzle or a pintle type nozzle.

A toroidal cavity or chamber it is formed wholly Within the piston. The diameter of this chamber is usually one-half or slightly more than one-half of the diameter of the piston, and its depth is usually approximately one-half its diameter. For best results the diameter of this chamber is such that the top of the piston surrounding the chamber is an annulus or considerable area, so that when the piston reaches the end of its compression stroke, a pronounced squish effect on the air confined between the piston, cylinder and head is produced, the piston having only a working clearance with the head, for example, .03 to .06".

As shown in Fig. 1, the chamber i is of urtform diameter for more than one-half depth and has rounded inner ends it which merge into a conically formed central projection it. Ac cording to the present invention, the projection iii is formed as a part of a plug il provided w l a shoulder i3 abutting the bottom of a counterbore it in the piston and having a shank 25 extending through a bore 28 concentric with the bore !9. The shank Ed is threaded to receive a nut 22 which engages the bottom of the head of the piston i and clamps the shoulder it fluid tight against the bottom of the bore iii. For insulating purposes the sides of the plug adjacent the bore 49 do not contact the same.

The plug 4'! is of suitable high heat resisting material such as a nickel-chromium alloy such as .Nichrome," or a cobalt, nickel, chromium steel alloy such as Stellite, or any other suitable metal alioy. The plug i! has a tubular centrally disposed cavity 23 formed therein extending upwardly through the projection IS with an outlet 26 opening into the central portion of the chamber hi and one or more inlets 25 connecting its closed end 26 with the bottom of the chamber ii. The walls of the cavity 23 may be conically inclined from the smaller outlet 24 to its larger closed end to aid in increasing the velocity of fluid flow from its outer end. The area of the outlet 2 is preferably at least equal to the combined area of the inlets 25. The inlets 25 are preferably disposed tangentially of the inner wall of the tube and in the same direction as the spiral swirl of in the chamber indicated by the arrows iii in Fig. 3.

In the form shown in Fig. 2 the fuel injector it is disposed at an angle between valves (not shown) and the chamber I4 is a torus. The conical projection it with its tubular cavity 23 having its outlet 2 t discharging into the central portion of the chamber hi and its inlet or inlets 25 disposed in line with the general direction of flow of gases in said chamber is formed as a part of a plug 23 of high heat resisting material having an annular base flange 29 abutting the annular shoulder 3 formed in the head of the piston and clamped thereagainst in sealed relation by a plug 3! in threaded engagement with the bore 32 in said piston. The upper part of the plug 28 where it passes through the bore 33 in the piston may be spaced therefrom for heat insulating purposes. The top of the piston has only a working clearance with the cylinder head though in some instances shallow valve clearance recesses may be formed in the piston top.

In compression pressure ignition engines having combustion chambers of the general forms shown in Figs. 1 and 2 but with solid bottom portions and utilizin a pronounced squish action and induction induced swirl, it has been found that during the last part of the compression stroke, the gases in the central portion of the open chamber have a purely rotational movement in a substantially horizontal plane, that above this portion the gases move spirally upwards toward the open end of the chamber and on reaching the opening travel in the same direction rotationally as the spiral how ever the piston crown. Beneath the central portion above referred to the gases move spirally downwards toward the bottom of the chamber and pass across the bottom to the center of the chamber in a spiral following the same direction as that of the spiral gas flow over the crown. This action is true whether the open chamber is of the form shown in Fig. l or in Fig. 2.

This invention makes use of the gas movement phenomena above descibed by forming the central portion of the chamber as a tube up which some of the gases may pass to the central portion of the chamber where they mix with the gases rotating in a substantially horizontal plane and then pass with these gases spirally toward the bottom and the top of the chamber. Since the tube or projection i6 is red hot or operating at a high temperature when fuel is introduced in the chamber is near the end of the compression strolce, the gases entering the cavity 23 will be mixed with a portion of the fuel charge which fuel carrying gases will burn readily either in the cavity or as they leave the outlet 24 and mix with the other gases and raise their temperature more quickly to the ignition point and thus reduce the ignition delay period, the tubular cavity 23 acting as a continuous flow burner. Since the cross-sectional area of the cavity .23 is small, its heat is readily imparted to the fuel carrying stream passing through it and also other gases contacting the outer hot walls of the projection is are heated thereby to an ignition temperature. The hot surface projection it also insures that a definite ignition point of the charge is located at the central portion of the chamber from which flaming gases are propagated into the streams of fuel laden gases passing upwardly and do wardly from the central zone of said chamber. These flaming gases help to break up the incoming fuel so that high injection pressures through small holes need not be necessary and pintle type r other coarser nozzles may be used. Also because oi"; the greater heat available with the tube, fuels with lower ignition quality than those usually employed in engines of this type may be used.

Referring to Fig. l, the general operation of the engine is, as follows: During the downward movement of the piston '1 on its induction stroke, the inlet valve 9 is opened and air is admitted into the cylinder 5 in a stream directed to produce a swirl as by the use of the mask it. On the upward stroke of the piston, this is con pressed, and as the piston nears the end of its compression stroke, the air between the annulus on the top of the piston and the head squeezed out and forced into the chamber i l in a spiral path of the same hand as the induced swirl and travels down to the central portion of the chamher where its movement is substantially t u rotary in a horizontal plane and some of the a then spirals down to the bottom of the chamber in the same direction as the initial swirl and moves inwardly over the bottom to the center of the chamber and then upwardly through the axis of the chamber to the central portion of the chamber while some of the air spirals upwardly from said central portion. As viewed in vertical cross section, the action of the air movement is indicated by the arrows A, B, C, D, and Near the end of the compression stroke, for example, ten degrees before top center, fuel is sprayed into the chamber id as indicated by the dotted. lines F. Some of the fuel that is carried down with the air into the lower part of the chamber passes through the port or ports 25 into the cavity 23 and moves upwardly to its outlet where as a flaming stream it meets the streams of fuel laden gases A. and D, and i nition is rapidly propagated through the charge. This action as the piston starts on its working stroke on which, after the termination of injection, the gases expand in the cylinder. The expanded gases are forced out or" the cylinder on the following stroke past the open exhaust valve H.

A plurality of equally circumfcrentially spacer passages for 63121131310, four or more, may be provided in the piston as shown Fig. l, which passages are preferably tangentially disposed relative to the curved bottom portion of the chamber is and open up into the annular top said piston. Under the squish action previously referred to these passages permit of the air being forced from the annulus a into the bottom portion of the chamber to assist upward swirl of the area from said bottom and also permit fuel laden air to reach the between the flat annulus of the piston and the cylinder to secure better distribution of the fuel.

While the above construction is preferred, some advantages might be obtained if the inlets 25 were omitted and part of the fuel introduced into the tube 23 from its open end, and I, therefore, desire it to be understood that this invention is not to be limited to the specific details of construction except as such limitations appear in the appended claims.

What I claim as my invention is:

1. In a compression ignition internal combustion engine of the type having its combustion chamber formed as an open toroidal chamber substantially wholly within the top of the piston into which fuel is injected near the end of the compression stroke, the air supplied to the engine cylinder having rotary swirl imparted to it and the chamber being spaced from the sides of the cylinder to provide a pronounced squish action to augment the rotary swirl as the piston during compression closely approaches the cylinder head, said chamber having a midportion measured vertically of the height of said chamber, the air in said chamber during compression having a sub stantially rotary movement about said midportion of said chamber substantially coinciding with a horizontal plane half way between the top surface of the piston and the bottom of the combustion chamber and rotary spiral movements in planes at substantially right angles to said horizontal plane, from said midportion toward the top and bottom portion of said chamber, that improvement which comprises forming the cen tral portion of the bottom of said chamber as a conical hot tube projection extending toward but not beyond the above defined midportion of said chamber and having a lengthwise extending axially alined tubular cavity which discharges into said midportion of the chamber in which the air has a substantially rotary movement.

2. The structure as defined in claim 1, in which the lower end of the tubular cavity has restricted communication with the lower part of the bottom of said chamber.

3. In a compression ignition internal combustion engine of the type having its combustion chamber formed as an open cavity with a curved bottom substantially wholly within the top of the piston into which fuel is injected near the end of the compression stroke, the air supplied to the engine cylinder having an induction induced swirl imparted to it and the chamber being spaced from the sides of the cylinder to pronounced squish action to augment the induction induced swirl as the piston during compression closely approaches the cylinder head, said chamber having a midportion measured vertically of the height of said chamber, the air in said chamber during compression having a substantially rotary movement in said midportion of said chamber substantially coinciding with a horizontal plane half way between the top surface of the piston and the bottom of the combustion chamber, and a spiral movement from said midportion towards the top and bottom of said chamber, that improvement which comprises a hot surface projection extending upwardly from the central portion of the bottom of said chamber and provided with a tubular lengthwise extending cavity which opens into said midportion of said chamber, and passages circumferentially spaced about the top of said piston and extending to the bottom of said chamber and tangentially disposed relative to the curved bottom of said chamber.

LOUIS O. FRENCH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,865,841 Cummins July 5, 1932 1,967,243 Hesselman July 24, 1934 2,071,062 Cummins Feb. 16, 1937 2,118,319 Maynard May 24, 1938 2,206,322 Huesby July 2, 1940 2,256,776 Kammer Sept. 23, 1941 2,505,999 Smith May 2, 1950 FOREIGN PATENTS Number Country Date 676,997 Germany June 16, 1939 

